Preface

In theory, nothing works, but everyone knows why. In practice, everything works but no one knows why. Here, we combine theory and practice; nothing works and no one knows why!

Learning computer science must always be a combination of theory and practice; you need to know what you're doing (theory), but you also need to know how to do it (practice). My experience of learning how to create web applications was that few teachers found a sweet spot for this balance; either I read pages and pages about inheritance, virtual environments, and test-driven development, wondering how it all applied to me, or I installed a bunch of tools and frameworks and libraries and watched the magic happen with no idea how it worked.

What follows is, I hope, a good balance. From the first chapter, you'll have a Flask web application running that the whole world can visit, which is quite practical even if it doesn't do anything but greet visitors with "Hello, World!". In the chapters that follow, we'll walk through building three interesting and useful projects together. In general, we'll build things ourselves wherever possible. While it's not good to reinvent the wheel, it is good to be exposed to a problem before you're exposed to the solution. Learning a CSS framework before you write a single line of CSS leaves you in a confused state, in which you would wonder, "But why do I actually need this?", and the same goes for many other frameworks and tools. So, we'll start from scratch, take a look at why it's difficult, and then introduce tools to make our lives easier. I think this is the ideal balance between theory and practice.

When I told people I was writing a book on Flask, the common response was "Why? There are already so many books and tutorials on Flask." This is a valid question, and the answer to it provides a nice outline for what to expect from this book. Flask By Example is different from other Flask educational material and here's why.

We won't leave you stranded

Many Flask tutorials show you how to develop a Flask application and run it locally on your own machine, and then they end. This is great as a first step, but if you're interested in building web applications, you probably want them to be accessible on the Web so that your friends, family, coworkers, and customers can admire your handiwork without popping by your house. From our first project onward, our applications will run on a Virtual Private Server (VPS) and be accessible to the world.

We won't build a blogging application

If you've read any web application development tutorials, you must have noticed that nearly every one of them is about how to build a blog using x and y. I'm pretty tired of the blog example (actually, I never want to see anyone show me how to build a blog again). Instead, you'll create some interesting, original, and possibly even useful projects while learning how to develop web applications with Flask.

We will focus on security

Cybercrime has become something of a buzzword of late. Arguably, the reason that we read about major web applications being hacked on an almost daily basis is because so many developers do not know about SQL Injection, CSRF, XSS, how to store passwords, and so many other things that should really be considered basic knowledge. As we develop the three projects in this book, we'll take the time to explain some core security concepts in detail and show you how to harden our applications against potentially malicious attackers.

We will give in-depth explanations

We won't just give you some code and tell you to run it. Wherever possible, we will explain what we're doing, why we're doing it, and how we're doing it. This means that you'll be able to take ideas from all of the projects, combine them with your own ideas, and get started with building original content right after working through this book.

Therefore, I hope that this book will be of use to you, no matter whether you are beginning to cut your teeth in the world of computer science and programming or have a computer science degree from a famous university and have compiler theory pouring out of your ears but now want to build something practical and fun. May you have as much fun working through the projects as I did while putting them together!